Alzheimer's disease is infamous for its devastating impact on memory, bringing significant mental and emotional stress to patients and their families.
Scientists at the company Cortexyme, working with academics from around the world, say the findings of their study could lead to new treatment options for Alzheimer's disease sufferers that work by targeting the bacterium Porphyromonas gingivalis, and they have developed a candidate drug that is now undergoing clinical trials.
They also showed that when genetically modified mice who were predisposed to Alzheimer's were infected with P. gingivalis, the bacterium ended up in their brain and that this was associated with increased levels of amyloid protein.
Scientists analysed brain tissue, spinal fluid, and saliva from dead and living patients with diagnosed and suspected Alzheimer's.
As BBC reports, there are some serious questions left to be answered.
"The idea that bacteria and viruses may play a part in brain disease like Alzheimer's is not necessarily new", Rebecca Edelmayer, Ph.D., director of scientific engagement for the Alzheimer's Association, told CBS News. "He points out that while most of the data presented in the Cortexyme study supported their hypothesis, gingipains weren't found in all of the Alzheimer's-affected brains, 'so whilst it may be a cause, the data don't exactly support it being the only cause". They then developed a group of substances created to block (inhibit) the action of gingipain and tested them on cells in the laboratory.
However, he welcomed the avenue of inquiry as no new drugs targeting Alzheimer's have been released for over 15 years. In preclinical experiments detailed in the paper, the researchers demonstrated that inhibition by COR388, the most promising compound in the series and the subject of Cortexyme's ongoing clinical development program, reduced the bacterial load of an established Pg brain infection, blocked Aβ42 production, reduced neuroinflammation, and protected neurons in the hippocampus, a part of the brain that mediates memory and frequently atrophies early in the development of AD.
However, he said the study was limited because the team has not yet determined if different strains of P. gingivalis are more virulent than others in causing brain infection.
The improvements were short-lived, however, lasting just one week.
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'Based on these findings, we believe that P. gingivalis is the main cause of Alzheimer's disease, and the gingipains are the main drivers of Alzheimer's pathology, ' Dominy says.
The findings, which were published in the January 14 issue of Nature Medicine, can potentially help with early Alzheimer's diagnoses and new drug development.
Now, scientists are saying they've got one of the most definitive leads yet for a bacterial culprit behind Alzheimer's, and it comes from a somewhat unexpected quarter: gum disease.
Traditional broad-spectrum antibiotics would probably be ineffective against P. gingivalis in the brain, according to the research.
There is now no test doctors can use to conclusively determine whether someone will get Alzheimer's disease and there are a lot of unknowns about its cause. "It really will be important to see how this plays out in human randomized controlled trials, which is the gold standard for understanding whether a therapeutic targeting something like the P. gingivalis mechanism would actually be effective", she said.
Howard Fillit, a neuroscientist and chief science officer at the nonprofit Alzheimer's Drug Discovery Foundation in New York City, is more impressed.
If the findings hold up, do they mean that everyone with a P. gingipains infection-nearly 50% of the US adult population-will develop Alzheimer's?
"I think the research really reinforces the complexity of Alzheimer's disease", she said.